Pulse tube refrigerator

ABSTRACT

A refrigeration apparatus including a pulse tube and regenerator operable with hydrogen gas and a compressor, the gas being cyclically flowed into and out of the pulse tube. The source of this gas and the compressor being a container of lanthanum nickel (LaNi5) which when cooled absorbs a large quantity of the gas, and when heated desorbs rapidly a large quantity of the gas which tends to expand the flows under pressure to the pulse tube where refrigeration is produced.

United States Patent [191 Daniels [11] 3,817,044 [4 June 18, 1974 PULSETUBE REFRIGERATOR [75] Inventor: Alexander Daniels, Briarcliff Manor,

[73] Assignee: North American Philips Corporation, New York, NY.

22 Filed: Apr. 4, 1973 21 Appl. No.: 347,814

[52] US. Cl. 62/6 [51] Int. Cl. F25b 9/00 [58] Field of Search 62/6 [56]References Cited UNITED STATES PATENTS 3,237,42! 3/1966 Gifford 62/62/1967 Smith ..62/6 4/1967 Green ..62/6

Primary ExaminerWilliam J. Wye Attorney, Agent, or Firm-Frank R. Trifari[57] ABSTRACT A refrigeration apparatus including a pulse tube andregenerator operable with hydrogen gas and a com- ,pressor, the gasbeing cyclically flowed into and out of the pulse tube. The source ofthis gas and the compressor being a container of lanthanum nickel (LaNiwhich when cooled absorbs a large quantity of the gas, and when heateddesorbs rapidly a large quantity of the gas which tends to expand theflows under pressure to the pulse tube where refrigeration is produced.

7 Claims, 3 Drawing Figures P'A'TENTEDJum m4 3. 8 17:. 044

Fag 1 lib Fag 1 5 5 l PULSE TUBE REFRIGERATOR BACKGROUND OF THEINVENTION The functioning of pulse tube refrigerators is known, however,numerous inherent structural and operational characteristics havegreatly reduced practical applications of these devices. As compared toStirling, Vuilleumier and Joule-Thompson type refrigerators, pulse tubesare relatively inefficient, one limitation resulting from thereciprocating-piston type compressors typically used to compress the gasflowed into these pulse tubes. Such compressors utilize inlet and outletvalves that produce a sine-wave pressure-v-time profile, the limitedarea under this sine-wave representing a limited work outout and workefficiency characteristic. To smooth-out or otherwise reduce themagnitude of the pressure-wave oscillation, and also to increase thearea under the pressure curve, a high-pressure storage chamber or bufierspace may be used intermediate the compressor outlet and the pulse tubeinlet. However, this additional component is objectionable, and does notsignificantly alter the basic operation.

Another problem with known pulse tube refrigerators is the considerablevibration and noise produced by associated compressors, which leads tothe burden and expense of either attenuating the vibration, orphysically separating the components, with perhaps a flexible tubeconnection. These compressors are relatively high-speed devices, thistype being chosen due to the belief that a high-speed operation isnecessary to obtain reasonable efficiency and that highercycles-perminute leads to higher efficiency, and because typicalelectric motors available and used to drive the compressors alwaysoperate at hundreds of revolutions or cycles per minute.

The new invention seeks to provide a pulse tube re frigerator that hasessentially no moving parts and consequently an absence of vibration andnoise, has a notable improvement in efficiencyover known pulse tubedevices, and that can operate with a power input that is merelyrelatively low temperature heat rather than a mechanical compressor andmotor drive.

SUMMARY OF THE NEW INVENTION It has been discovered that high efficiencyis possible with a very slow cycle, even perhaps one cycle per minuteversus 400 c.p.s. of the prior art. This is accomplished by using alanthanum-nickel (LaNi compressor which can produce a pressure wave inhydrogen gas that approaches a very efficient square-wave shape versus asine-wave shape of the reciprocating compressors. The new compressor incombination with an enlarged pulse tube will have an overall efficiencythat renders the apparatus practical, particularly at temperatures closeto K, the boiling point of hydrogen. Additionally, the LaNi compressorhas essentially no moving parts, and thus eliminates substantially allof the prior vibration and noise problems.

The new compressor includes within a container a quantity of LaNi thathas the capability of readily absorbing hydrogen gas when cooled, andwhen heated readily desorbing the gas which expands and flows underpressure. Only heat energy is required to produce the pressure in thegas, in contrast to a typical system of an electric-motor and compressoror other external power; noise, compressor, maintenance, vibra tion,wear, and even waste heat are all greatly reduced or eliminated. It isanticipated that the generally square-wave pressure profile will permita 10 to 15 percent increase in efficiency of the new device overreciprocating-piston compressor-pulse tube refrigeration systems. Theamount of heat transferred is related to the dwell time at peak pressuresuch that a square wave has the longest high-pressure time period.

This invention would have useful applications where either long,maintenance-free life isrequired, or where there is a requirement forextremely low vibration and- /or accoustical noise, or where only heatenergy rather than mechanical power is available. The new system isdesigned for use with hydrogen, partly because this gas is the one whichis operable with the lanthanum-nickel compressor, and partly because thehydrogen boiling point of 204 Kelvin establishes a desirable lowtemperature zone at which refrigeration can be achieved with thisapparatus.

A preferred embodiment of the invention will now be described withrespect to the drawings listed below.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing of aLaNi pulse tube refrigerator of the new invention.

FIG. 2 is a pressure-v-time diagram of the hydrogen gas in a pulse-tuberefrigeration cycle, using a reciprocating-piston compressor.

FIG. 3 is a pressure-v-time diagram of the hydrogen gas in a pulse-tuberefrigeration cycle using a LaNi compressor.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the new invention10 which includes containers 11 and 12, both of which contain quantitiesof LaNi shown as 13 in FIG. 1. Container 11 has associated with it aheating means 14 which may take the form of electrical or fluid heatingelement 140, with associated valve or control switch 17a, and acorresponding, similar heating element 14b in container 12 with itsassociated valve or control switch 17b. A cooling means 15 is providedwith elements 16, 16a within each of said containers, and a valve means17 for controlling fluid flow through one or the other elements 16 and16a. When cooled the LaNi within these containers has the capacity toabsorb a large quantity of hydrogen gas. Later in operation it is thecharacteristic of this device that the LaNi material when heated willdesorb the large quantity of hydrogen at a very rapid rate. Morespecifically, at specific temperatures the hydrogen is discharged andproduces corresponding pressures.

Manifold l8 and valve 19 are provided to interconnect containers l1 and12 in parallel or series as desired for power, speed, and efficiency. Inparallel both containers at once can discharge the hydrogen gas duringthe desorption period, and later both can simultaneously absorb thehydrogen gas during the absorption period. In series valve 19interconnects the compressor outlet 20 with inlet 21 of regenerator 29,while compressor inlet 22 is closed; alternatively valve 19 conmeets thecompressor inlet 22 with the regenerator port 21 while valve 20 isclosed. In this way for example, one container can be cooled while theother is heated.

The pulse tube 23 has a cold end 24 with freezer part 25, and an inletend 26 with a cooler-heat-exchanger 27. The pulse tube body is formed ofa stainelss steel tube 28, while the parts 25 and 27 are made of copperfor good heat exchange properties.

In operation hydrogen gas which is compressed and somewhat heated, isflowed to the regenerator wherein a quantity of heat is extracted andstored; the compressed hydrogen then flows through cooler 27 whichextracts a further quantity of heat and transmits same to the outsideenvironment; the hydrogen then flows into the pulse tube where itexpands to its lowest temperature in the freezer portion 25. The objectto be cooled receives cold through a heat exchanger 25a of the freezer.Subsequently valves 17a, 17b and 19 are adjusted such that heat isdiscontinued to elements 14a, 14b, and the cooling means 15 is actuated.Hydrogen then flows backward from the pulse tube 23 through theregenerator 29 and into one or more of the compressor containers 11 and12. The gas leaving the chamber of the pulse tube is reheated somewhatupon passing through the regenerator 29 such that when it returns to thecompressor it is absorbed at the heated temperature, and later duringcompression does not have to be heated up from a cold condition butmerely from the warm condition.

According to FIG. 3 the pressure profile that is produced in thehydrogen gas on being desorbed from the hydrogen compressor follows thesomewhat squared sinusoidal curve shown. This is in contrast to theregular sine-wave pattern of FIG. 2 which shows the pressure variationthat occurs with time from a typical reciprocating mechanicalcompressor. Consequently, when hydrogen flows according to the generallysquare wave pressure profile of FIG. 3, the resulting operation of thepulse tube is more efficient than gas flow according to a sinusoidalpressure wave form of FIG. 2.

A great variety of structural configurations could be used within thescope of this invention. For example, six containers of LaNi might beused in series with an approximate cycle time of one minute.Furthermore, any other materials having the capability of LaNi forabsorbing and desorbing a gas, or any gas other than hydrogen similarlyoperable with LaNi would also be within the scope of this invention.

I claim:

1. A closed refrigeration system comprising a pulse tube operable with acyclic input flow and discharge flow of hydrogen gas to producerefrigeration, at least one container having a quantity ofLanthanum-nickel (LaNi therein, a quantity of hydrogen gas in saidsystem, means for heating said LaNi means for cooling said LaNi ductmeans interconnecting said container and said pulse tube, first valvemeans for selectively controlling flow of hydrogen gas in said ductmeans, a regenerator intermediate said pulse tube and said container,whereby heating said LaNi causes same to desorb hydrogen gas which flowsunder pressure through said duct means and flows through saidregenerator which absorbs heat from the gas, and flows into said pulsetube which produces refrigeration, and whereby cooling said LaNi causessame to absorb hydrogen gas which is drawn to flow back from said pulsetube through said regenerator which returns certain heat to said gas, tosaid container where the LaNi absorbs the hydrogen.

2. Apparatus according to claim 1 wherein said means for cooling theLaNi comprises a tubular cooling element within said container, and asource of cooling fluid flowed through said cooling element forreceiving heat from said LaNi within the container.

3. Apparatus according to claim 1 wherein said means for heating theLaNi comprises at least one electrical heating element within saidcontainer, and a source of electric current flowed into said element forheating same.

4. Apparatus according to claim 1 comprising at least two of saidcontainers, said duct means interconnecting the containers, said firstvalve means controlling hydrogen flow in said duct means selectively toprovide series or parallel connection between said containers.

5. Apparatus according to claim 1 wherein said pulse tube comprises astainless steel tubular housing having an inlet end in communicationwith said regenerator and a remote end, the inlet end having an exposedcopper part operating as a cooler and the remote end having a copperpart operating as a freezer.

6. A pulse tube refrigerator in combination with a lanthanum-nickel(LaNi hydrogen gas compressor and operable with a quantity of hydrogengas, the compressor comprising at least one container of LaNi firstmeans for heating said LaNi second means for cooling said LaNi ductmeans communicating said container with said pulse tube for flowinghydrogen gas between said container and pulse tube, a regenerator insaid duct means intermediate the container the pulse tube, valve meansfor controlling flow of hydrogen gas in said duct means, whereby heatfrom said first means causes the LaNi to desorb hydrogen gas to flow viathe duct means through the regenerator and into the pulse tube whenrefrigeration is produced, and cold from said second means causes saidLaNi to absorb said gas by drawing same via said duct means back fromthe pulse tube through the regenerator.

7. Apparatus according to claim 1 wherein said means for heating andmeans for cooling the LaNi and respectively causing the hydrogen gas tobe cyclically desorbed and absorbed, causes this gas to experience apressure-vs-time variation that approximates a square wave.

73333 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,317,044 Dated June 18, 1974 lnv nwrwx ALEXANDER DANIELS It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Col. 2, line '41 After "17b. insert -Valves 'lla, llb,

12a, and 12b control the flow of LaNi into and out of containers 1i andl2.--

Signed and sealed this 1st day of October 1974,

Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents

2. Apparatus according to claim 1 wherein said means for cooling theLaNi5 comprises a tubular cooling element within said container, and asource of cooling fluid flowed through said cooling element forreceiving heat from said LaNi5 within the container.
 3. Apparatusaccording to claim 1 wherein said means for heating the LaNi5 comprisesat least one electrical heating element within said container, and asource of electric current flowed into said element for heating same. 4.Apparatus according to claim 1 comprising at least two of saidcontainers, said duct means interconnecting the containers, said firstvalve means controlling hydrogen flow in said duct means selectively toprovide series or parallel connection between said containers. 5.Apparatus according to claim 1 wherein said pulse tube comprises astainless steel tubular housing having an inlet end in communicationwith said regenerator and a remote end, the inlet end having an exposedcoPper part operating as a cooler and the remote end having a copperpart operating as a freezer.
 6. A pulse tube refrigerator in combinationwith a lanthanum-nickel (LaNi5) hydrogen gas compressor and operablewith a quantity of hydrogen gas, the compressor comprising at least onecontainer of LaNi5, first means for heating said LaNi5, second means forcooling said LaNi5, duct means communicating said container with saidpulse tube for flowing hydrogen gas between said container and pulsetube, a regenerator in said duct means intermediate the container thepulse tube, valve means for controlling flow of hydrogen gas in saidduct means, whereby heat from said first means causes the LaNi5 todesorb hydrogen gas to flow via the duct means through the regeneratorand into the pulse tube when refrigeration is produced, and cold fromsaid second means causes said LaNi5 to absorb said gas by drawing samevia said duct means back from the pulse tube through the regenerator. 7.Apparatus according to claim 1 wherein said means for heating and meansfor cooling the LaNi5 and respectively causing the hydrogen gas to becyclically desorbed and absorbed, causes this gas to experience apressure-vs-time variation that approximates a square wave.